An air cleaner is a device configured to filter dust or foreign matter from air through a filter disposed in an air flow passage while inducing forcible flow of air. A typical air cleaner is configured to collect dust through the filter and to remove a toxic gas from air in various ways.
In the air cleaner, air purification is typically performed through sequential dust collection using a pre-filter configured to filter large dust particles and a HEPA-filter configured to filter fine dust particles. This arrangement prevents such a relatively expensive HEPA filter from suffering shortened lifespan due to filtration of large dust particles.
The air cleaner may be provided with a filter for removal of a toxic gas. Among various methods for removing a toxic gas, activated carbon is generally used to remove a toxic gas from air by allowing the activated carbon to adsorb the toxic gas.
In another method, a photocatalytic material is activated through irradiation with light and air is forced to flow around the activated photocatalytic material to remove a toxic gas therefrom through photocatalytic reaction. As the photocatalytic material, titanium oxide (TiO2) is generally used in the art.
When irradiated with UV light, titanium oxide is activated and causes photocatalytic reaction, and in recent years, a photocatalytic material capable of reacting in the visible range has been developed due to harmfulness of UV light and the like.
Such a photocatalytic material obtains activation energy from light. Thus, a photocatalytic material activated by UV light requires UV irradiation. Thus, upon irradiation of the photocatalytic material with UV light, a light source is necessarily separated from the photocatalytic material by a predetermined distance.
However, a typical domestic or small air cleaner has a structure in which filters are stacked to overlap each other and a fan is disposed at the rear side thereof. With such a structure, the air cleaner is restricted to a planar and flat shape. Thus, it is not easy for such an air cleaner to have a space for installation of the photocatalytic material and the light source. That is, since a typical domestic or small air cleaner generally has a planar and flat shape, a photocatalytic filter is not suitable for such an air cleaner.
Therefore, in order to apply the photocatalytic filter to such a domestic or small air cleaner, the air cleaner must be designed in consideration of an air flow passage, air suction and discharge directions, a filter installation structure, a relationship between an installation direction of filters and an air flow direction, an installation location of a light source, and the like.
In addition, in the structure wherein a UV light source and a photocatalytic filter are installed in a small air cleaner, it is necessary to adjust characteristics of UV light and the photocatalytic filter so as to secure sufficient effects of UV light and the photocatalytic filter.
On the other hand, such a typical domestic or small air cleaner is generally provided with a sensor for measuring the amount of dust in air or a toxic gas in air. However, as described above, since the domestic or small air cleaner has a flat shape and includes filters stacked to overlap each other, the air flow passage inside the housing has an insufficient space for installation of the sensor and is not suitable as a sensor installation location since air flows into the air flow passage after passing through the filter.
Conventionally, the sensor is disposed outside the housing to measure air quality. However, in this structure, since the intensity of light varies due to an illumination difference or a difference between day and night, the degree of light scattering differs even in the same amount of dust, thereby making it difficult for the sensor, which is configured to measure the amount of based on the degree of light scattering, to measure an accurate amount of dust.
Next, when the sensor for detecting toxic gases is disposed outside the housing, the sensor cannot accurately measure a toxic gas floating above air or sinking due to a lighter or heavier weight than the air, and can measure only a toxic gas present near the sensor, thereby failing to provide a suitable function of the sensor.